This invention relates to medicaments for use in the treatment of disorders of the middle ear.
It is important to maintain the patency of the Eustachian tubes of the ear since failure to do so can lead to a number of clinical disorders. Blockage of the Eustachian tubes often occurs in persons experiencing discomfort arising from changes in ambient pressure, such as aviators and divers, and this can lead to pain and damage to the hearing. Partial or total blockage of the Eustachian tube can potentiate the onset of serous otitis media (more commonly known as glue ear), which is a very common disorder in children in the age range of about 7 to 12. This can cause partial deafness leading to lack of attention in school and developmental problems.
Currently, the only available procedure for dealing with the problem of glue ear is to fit grommets or ventilation tubes, although antibiotics can offer short-term relief. Grommets are small plastic tubular inserts which require to be inserted by a surgical procedure involving an incision in the tympanic membrane. The procedure has disadvantages, quite apart from the need for a surgical procedure, including the risk of infection in the middle ear arising from direct contact with a contaminated environment and the requirement that the patient must avoid getting water in the treated ear, thus excluding the child from all aquatic activities. A further problem is that grommets tend to fall out.
It is also believed that the exudation of serous fluid can cause plug formation to occur in the Eustachian tube in adults which can cause obstruction to air flow and thus prevent ventilation of the middle ear. This problem has major implications in underwater diving activities, aviation and emergency escape from submarines. This is also an area which is addressed by the present invention.
The present invention is based upon the belief that in the healthy natural ear, the surfaces of the Eustachian tubes contain a natural lining or coating which provides easy release, thus preventing or deterring the surfaces of the tubes from sticking together. The present invention, therefore, seeks to overcome the problems discussed above by administering a medicament capable of providing the same kind of action as the natural release agent in circumstances where the natural release agent has failed or is not deficient.
According to one aspect of the present invention there is provided use of a surface active agent composition in the preparation of a medicament as a prophylactic or for treatment of disorders of the middle ear by administration to the Eustachian tube of the medicament, said composition including a component capable of persisting on the surface of the Eustachian tube for an extended period of time.
Preferably, the surface active agent should be capable of persisting on the surface of the Eustachian tube for at least about 3 months, preferably at least 6 months, so that the tube will retain a surface active layer over such an extended period and will be less likely to block. Surface active agents are preferably solid and capable of forming an adherent layer on the surface of the tube. A physical or chemical binding of the surfactant to the surface of the Eustachian tube is highly desirable. The surface active agent may be selected from a variety of materials but should have a very low level of toxicity. Examples of suitable surface active agents are soaps, e.g. a fatty acid salt, such as magnesium stearate. Preferred surface active agents include surface active phospholipids, such as diacyl phosphatidyl cholines (DAPC""s), e.g. dipalmitoyl phosphatidyl choline (DPPC); dioleyl phosphatidyl choline (DOPC) and distearyl phosphatidyl choline (DSPC). It is also preferred to include a spreading agent in the composition to assist the DPPC or analogous compound rapidly to form a thin film over the surface of the Eustachian tube. A number of agents are capable of acting in this way including other phospholipids, such as phosphatidylglycerols (PG); phosphatidylethanolamines (PE); phosphatidylserines (PS) and phosphatidylinositols (PI). Another useful spreading agent is cholesteryl palmitate (CP).
According to another aspect, therefore, the present invention comprises use of a surface-active phospholipid (SAPL) composition in the preparation of a medicament as a prophylactic or for treatment of disorders of the middle ear, by administration to the Eustachian tube (or its aural end) of the SAPL composition in finely-divided solid form, said composition including a component capable of binding to the surface of the Eustachian tube.